Posted by
gm3sek on
Jun 30, 2018; 8:09am
URL: http://elecraft.85.s1.nabble.com/K3-factory-upgrade-to-K3-s-tp7642388p7642542.html
Al, thank you for pointing this out.
To my surprise, the reason for the difference between Al's
interpretation and mine is that there are *two different versions*
of the ARRL review of the KSYN3A, both available on the arrl.org
website. The version retrieved appears to depend on the search route
taken.
My message posted on Wednesday 27th June was based on the weblink
referenced within the message. In that version, Figure 10 shows a
very distinct phase noise advantage for the older KSYN3 at wider
frequency offsets.
However, the version accessed by Al is *different*. In this second
version, Figures 10 and 11 both show much lower levels of phase
noise from the KSYN3A at wider frequency offsets. (That appears to
be the only change, that Figures 10 and 11 have been quietly
replaced.) Based on this second version, I would agree with Al that
there is no significant difference in phase noise between the KSYN3
and KSYN3A at wider offsets.
In view of the uncertainly between the two different sets of
published results for wider frequency offsets, it seems best to
withdraw my message posted on Wednesday 27th June.
Thanks once again to Al W6LX for pointing this out.
73 from Ian GM3SEK
>-----Original Message-----
>From:
[hidden email] [mailto:elecraft-
>
[hidden email]] On Behalf Of Al Lorona
>Sent: 29 June 2018 22:47
>To: Ian White;
[hidden email]
>Subject: Re: [Elecraft] [K3] factory upgrade to K3(s)
>
>I'm not sure I agree with the exact numbers, Ian. I'm looking at
the
>review from Nov 2015 QST (from the Product Review archive on
>www.arrl.org ) and it appears that the difference in phase noise
>between old and new synths is closer to about 3 dB (difficult to
tell from
>the graph) beginning at offsets of *50 or 100 kHz*, not the 6 kHz
you
>cited. At 6 kHz the new still beats the old by almost 20 dB!
>
>So, while the old synthesizer certainly exhibits lower transmitted
phase
>noise out beyond 50 kHz offset, the new one is within a few dB of
it,
>and at 50 MHz both seem to meet the -130 dBc/Hz limit you cited.
>
>Al W6LX
>
>
>
>________________________________
>From: Ian White <
[hidden email]>
>To:
[hidden email]
>Sent: Wednesday, June 27, 2018 2:45 PM
>Subject: Re: [Elecraft] [K3] factory upgrade to K3(s)
>
>
>
>>A big reduction in receiver noise floor and a huge improvement in
>both
>>transmit and receive phase noise.
>
>That is far too simplistic. Anyone's personal definition of "the
>better synthesizer" will depend on what range of frequency offsets
>is more important for their particular type of operating.
>
>For HF CW in particular, phase noise at small frequency offsets is
>of paramount importance and I wouldn't argue with Don's report of
"a
>huge improvement in both transmit and receive phase noise" - but
>*only* in that specific context. There are also several other
>advantages that are relevant to high-performance HF CW that could
>also justify upgrading to the KSYN3A.
>
>At close frequency offsets from the carrier, the KSYN3A does indeed
>offer a large reduction in phase noise compared with the KSYN3
>(which itself was already good). But at wider frequency offsets,
>that situation reverses. According to the ARRL review [1], at all
>offsets beyond about 6kHz, the older KSYN3 continues to have a
lower
>noise floor than the newer KSYN3A "upgrade".
>
>Performance at wider frequency offsets, 10-100kHz and beyond, is of
>much greater importance in VHF-UHF contesting. This due to a
>combination of factors. The strongest signals at VHF-UHF are often
>much stronger than on HF, due to the use of high-gain beam
antennas;
>and also the weakest signals are *always* much, much weaker due to
>the lower levels of natural background noise. These two features
>stretch the requirement for dynamic range on VHF-UHF far beyond
>those for which most HF transceivers are designed.
>
>Anyone transmitting wideband phase noise has a much greater risk of
>raising the noise floor of many other stations across the whole
>contesting segment of the VHF or UHF band. Running the numbers
>reveals that anyone aiming to be a Big Gun in VHF contests has a
>responsibility to keep their wideband transmitted noise floor below
>about -130dBc/Hz at frequency offsets of 50kHz and more [2]. This
>can be a major engineering challenge, and the performance of the
>transceiver is almost always the most important building block.
>
>The KSYN3A just about meets the -130dBc/Hz noise floor target at
>frequency offsets of 10kHz or more... but according to the ARRL
>review [1] the older KSYN3 achieves it much more comfortably, with
>10-15dB to spare.
>
>I have both a K3S and a very early-model K3. The K3S (with the
>KSYN3A, of course) is used for HF contesting where smaller
frequency
>offsets are important. Meanwhile the old K3 is now used as a
>transverter driver for 144MHz and above - and for that particular
>purpose there are very good reasons *not* to replace the original
>KSYN3.
>
>73 from Ian GM3SEK
>
>
>[1]
>
http://www.arrl.org/files/file/ProductReviewsForDeb/2015/pr112015.p>d
>f
>
>[2]
>
https://thersgb.org/members/publications/video_archive.php?id=5703>Sorry, this talk is accessible only to RSGB members, but in a few
>words...
>
>G8DOH runs the numbers to demonstrate that the -130dBc/Hz target
>for transmitted phase noise is necessary to avoid raising the noise
>floor of other stations many kilometres away, and also many tens to
>hundreds of kHz away across the band, whenever their high-gain
beams
>happen to be pointed at each other.
>
>That calculation assumes the UK transmitter power limit of 400W PEP
>output. For the US power limit of 1500W output, keeping all other
>assumptions the same, the target for transmitted noise floor would
>need to be better than -135dBc/Hz. The older KSYN3 can still meet
>that more stringent target but the KSYN3A probably cannot.
>
>
>>-----Original Message-----
>>From:
[hidden email] [mailto:elecraft-
>>
[hidden email]] On Behalf Of Don Wilhelm
>>Sent: 27 June 2018 14:23
>>To: hawley, charles j jr; Charlie T
>>Cc:
[hidden email]
>>Subject: Re: [Elecraft] [K3] factory upgrade to K3(s)
>
>>
>>Chuck,
>>
>>A big reduction in receiver noise floor and a huge improvement in
>both
>>transmit and receive phase noise. It is like getting a new
>transceiver.
>>
>>If you are strictly a casual operator, those qualities may not be
>>important to you, but if you are a DX'er or a contester, or
>otherwise
>>operate in crowded band condition, those things should be
important
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